1. Field of the Invention
The invention relates to a welded vehicle wheel with a rim connected to a wheel disc.
2. Description of the Prior Art
Generally, a welded vehicle wheel is produced by connecting an outer ring-shaped circumferential part of a center or wheel disc to an interior bed region of a rim by a pressure seat, and then welding a front of the outer ring-shaped circumferential part along the interior bed region of the rim with a welded seam. Depending on the intended use, the welded seam may comprise a single continuous welded bead or may comprise several welded bead sections. A problem of this prior art wheels is that residues of machine oil and/or cleaning agents that are deposited on the center and rim during cold forming evaporate very quickly during welding and build up a high internal pressure between the center and the rim during production of the prior art wheel. The gaseous reaction products may also penetrate the molten part of the weld and form undesired pores and/or gas bubble inclusions that diminish the fatigue strength of the welded seam. This problem may be avoided by thoroughly cleaning and drying the rim and the wheel disc before establishing the pressure seat connection. Another problem is that high friction forces are created during production of the pressure seat connection and lead to impermissible metal wear in the area of the pressure seat. Reducing the oversize of the wheel disc to lower the friction forces is not a satisfactory solution, because doing so sharply diminishes the effect of the pressure seat and places the welded seam under greater stress. In the worst case, a break of the welded seam can result.
To avoid the undesired formation of pores and/or gas bubble inclusions during connection welding between the rim and the center, German reference DE 43 38 616 A1 provides wedge-shaped recesses arranged at a distance from one another on the outer circumferential part of the center. These recesses allow the gaseous reaction products created during welding to escape. The problem of this proposal is that the gaseous reaction products are able to escape only at discretely arranged points, and that producing the recesses requires an extra work step.
U.S. Pat. No. 5,417,476 discloses another solution. In this design, nobby strips that extend around the circumference are impressed in the outer circumferential part of the center and rest on the inner side of the rim. A space between two sequentially arranged strips in a manner similar to the recess, for the escape of the gaseous reaction products. However, the escape of the gaseous reaction products is hindered because the frontal area of the outer circumferential part also rests on the inner side of the rim. Depending on the nature of the surface and the pressing pressure, this contact may produce a tight metal seal. Another problem with this arrangement is this type of contact creates an undefined seat between the circumferential part of the center and the rim.
Japanese reference JP 07304301 A discloses that the gaseous reaction products created during welding are extracted via ring grooves in the rim and the circumferential part of the center. The ring grooves partially overlap in the axial direction so that in the circumferential direction a continuous gap is created between the inner side of the circumferential part and the point or welded seam. The circumferential part thereby rests only in an axially narrow zone of its outer starting region on the bed region of the rim in the form of a pressure seat connection. Producing the ring grooves requires an extra work step.